The primary purpose of this study is to evaluate the gastric emptying characteristics of glycerol (G) mixed with standard oral rehydration solution (ORS) (carbohydrate (CHO) (6-8%) and low concentrations of electrolytes (eg. NA+ 10 meg) during constant load submaximal exercise. A second purpose of the study is to evaluate the effects of G hydration on plasma volume (PV) both before and during exercise.